Showing papers on "Bandwidth (signal processing) published in 2013"

Beamspace MIMO for Millimeter-Wave Communications: System Architecture, Modeling, Analysis, and Measurements

Abstract: Millimeter-wave wireless systems are emerging as a promising technology for meeting the exploding capacity requirements of wireless communication networks. Besides large bandwidths, small wavelengths at mm-wave lead to a high-dimensional spatial signal space, that can be exploited for significant capacity gains through high-dimensional multiple-input multiple-output (MIMO) techniques. In conventional MIMO approaches, optimal performance requires prohibitively high transceiver complexity. By combining the concept of beamspace MIMO communication with a hybrid analog-digital transceiver, continuous aperture phased (CAP) MIMO achieves near-optimal performance with dramatically lower complexity. This paper presents a framework for physically-accurate computational modeling and analysis of CAP-MIMO, and reports measurement results on a DLA-based prototype for multimode line-of-sight communication. The model, based on a critically sampled system representation, is used to demonstrate the performance gains of CAP-MIMO over state-of-the-art designs at mm-wave. For example, a CAP-MIMO system can achieve a spectral efficiency of 10-20 bits/s/Hz with a 17-31 dB power advantage over state-of-the-art, corresponding to a data rate of 10-200 Gbps with 1-10 GHz system bandwidth. The model is refined to analyze critical sources of power loss in an actual multimode system. The prototype-based measurement results closely follow the theoretical predictions, validating CAP-MIMO theory, and illustrating the utility of the model.

A holistic view on hyper-dense heterogeneous and small cell networks

Abstract: The wireless industry has been experiencing an explosion of data traffic usage in recent years and is now facing an even bigger challenge, an astounding 1000-fold data traffic increase in a decade. The required traffic increase is in bits per second per square kilometer, which is equivalent to bits per second per Hertz per cell × Hertz × cell per square kilometer. The innovations through higher utilization of the spectrum (bits per second per Hertz per cell) and utilization of more bandwidth (Hertz) are quite limited: spectral efficiency of a point-to-point link is very close to the theoretical limits, and utilization of more bandwidth is a very costly solution in general. Hyper-dense deployment of heterogeneous and small cell networks (HetSNets) that increase cells per square kilometer by deploying more cells in a given area is a very promising technique as it would provide a huge capacity gain by bringing small base stations closer to mobile devices. This article presents a holistic view on hyperdense HetSNets, which include fundamental preference in future wireless systems, and technical challenges and recent technological breakthroughs made in such networks. Advancements in modeling and analysis tools for hyper-dense HetSNets are also introduced with some additional interference mitigation and higher spectrum utilization techniques. This article ends with a promising view on the hyper-dense HetSNets to meet the upcoming 1000× data challenge.

Fundamentals of wireless communications

Abstract: Radio Frequency (RF) communications are an important smart grid enabler for functions such as volt/VAR control, recloser control, and feeder restorations and isolation. This paper will give a basic tutorial on the types of radio frequency communications and the benefits and liabilities of each. Specific topics to be explored will be licensed verses unlicensed frequencies, distance between remote radios and base stations, and communications architectures. Radio technology is often referred in numerical ranges or frequencies. The decision on which frequency to employ in a network depends on a few key variables. Prior to deciding which frequency for a network, the application for the radio use will assist with dictation of which frequency range to utilize. Applications such as recloser control and volt/Var control may require a radio device that can provide a high bandwidth/fast speed solution. Other SCADA applications such as sensor monitoring may only require small bandwidth and for data delivery to be at a much slower speed. Another variable when deciding on a radio network is the distance from the main SCADA hosts to end remote devices such as RTUs or PLCs. Lower end frequencies (100 MHz-900 MHz) provide further coverage and greater distance from base stations/Access Points to remote end devices, whereas higher frequencies (2.4 GHz-5.8 GHz) provide shorter distance coverage, but higher bandwidth and relay data back to SCADA hosts much faster. Determining a network's architecture should focus on either the desire of a private, licensed network or the notion of an unlicensed, less expensive network. The lower licensed frequency ranges (100 MHz, 200 MHz, 400 MHz and upper 900 MHz bands) are often referred to as MAS (Multiple Address Systems) networks and require license acquisition from the FCC once geographical coverage is determined. These licenses are granted for the lower frequencies as mentioned previously but are considered the proprietary use of the owner. Anyone operating in these frequencies will be fined/cited by the FCC. The less expensive, unlicensed network is allowable for frequencies ranging from 902 MHz-928 MHz, which is defined as the ISM (Industrial, Scientific, and Medical) bands. Within the unlicensed frequency band, there exist registered bands (3.65 GHz) that employ WiMax (Wireless Microwave Access for Broadband) technology that provide shorter coverage for remote devices, however, the bandwidth and speed provided by these frequencies make them just as popular for networks. Further analysis and discussion of licensed versus unlicensed radio wireless communications is proposed in this paper.

Event-Based Sensor Data Scheduling: Trade-Off Between Communication Rate and Estimation Quality

Abstract: We consider sensor data scheduling for remote state estimation. Due to constrained communication energy and bandwidth, a sensor needs to decide whether it should send the measurement to a remote estimator for further processing. We propose an event-based sensor data scheduler for linear systems and derive the corresponding minimum squared error estimator. By selecting an appropriate event-triggering threshold, we illustrate how to achieve a desired balance between the sensor-to-estimator communication rate and the estimation quality. Simulation examples are provided to demonstrate the theory.

Investigation and Active Damping of Multiple Resonances in a Parallel-Inverter-Based Microgrid

Abstract: This paper addresses the resonance problem in a parallel-inverter-based grid-interactive microgrid. Unlike the single grid-connected inverter system where the resonance frequency is mainly fixed by the inverter output LCL filter parameters, the parallel-inverter-based grid-interactive microgrid system presents a more challenging picture where inverter interactions will excite complex resonances at various frequencies. As a result, line currents of inverters can be severely distorted even when the control schemes and filter circuits are properly designed based on the single-inverter model. This paper first develops a microgrid model using discrete time-domain closed-loop Norton's equivalent circuit. Multiple resonances can then be evaluated with the developed model. To improve the microgrid power quality, this paper also designs a virtual-harmonic-resistance-based active damping method. The proposed damping method can be seamlessly incorporated into the conventional deadbeat control scheme through the direct control reference modification. Therefore, the active damping method is able to address both the transient and steady-state resonances within the deadbeat current control bandwidth. Simulation and experimental results are provided to validate the correctness of the developed resonance modeling and active damping methods.

Terahertz wireless communications based on photonics technologies

Abstract: There has been an increasing interest in the application of terahertz (THz) waves to broadband wireless communications. In particular, use of frequencies above 275 GHz is one of the strong concerns among radio scientists and engineers, because these frequency bands have not yet been allocated at specific active services, and there is a possibility to employ extremely large bandwidths for ultra-broadband wireless communications. Introduction of photonics technologies for signal generation, modulation and detection is effective not only to enhance the bandwidth and/or the data rate, but also to combine fiber-optic (wired) and wireless networks. This paper reviews recent progress in THz wireless communications using telecom-based photonics technologies towards 100 Gbit/s.

Hybrid precoding for millimeter wave cellular systems with partial channel knowledge

Abstract: Next-generation cellular standards may leverage the large bandwidth available at millimeter wave (mmWave) frequencies to provide gigabit-per-second data rates in outdoor wireless systems. A main challenge in realizing mmWave cellular is achieving sufficient operating link margin, which is enabled via directional beamforming with large antenna arrays. Due to the high cost and power consumption of high-bandwidth mixed-signal devices, mmWave beamforming will likely include a combination of analog and digital processing. In this paper, we develop an iterative hybrid beamforming algorithm for the single user mmWave channel. The proposed algorithm accounts for the limitations of analog beamforming circuitry and assumes only partial channel knowledge at both the base and mobile stations. The precoding strategy exploits the sparse nature of the mmWave channel and uses a variant of matching pursuit to provide simple solutions to the hybrid beamforming problem. Simulation results show that the proposed algorithm can approach the rates achieved by unconstrained digital beamforming solutions.

To Transmit or Not to Transmit: A Discrete Event-Triggered Communication Scheme for Networked Takagi–Sugeno Fuzzy Systems

Abstract: This paper first proposes a discrete event-triggered communication scheme for a class of networked Takagi-Sugeno (T-S) fuzzy systems. This scheme has two main features: 1) Whether or not the sampled state should be transmitted is determined by the current-sampled state and the error between the current-sampled state and the latest transmitted state. Compared with those in a periodic time-triggered communication scheme, the communication bandwidth utilization is considerably reduced while preserving the desired control performance; and 2) it is a discrete event-triggered communication scheme due to the fact that the triggered conditions are only measured and checked at a constant sampling period. Compared with a continuous event-triggered communication scheme, the special hardware for continuous measurement and computation is no longer needed. Second, a networked T-S fuzzy model is delicately constructed, which not only considers nonuniform time scales in the networked T-S fuzzy model and the parallel distributed compensation fuzzy control rules but includes the aforementioned state error as well. Third, a stability criterion and a stabilization criterion about the networked T-S fuzzy system are derived, respectively. The stability criterion and stabilization criterion can provide a tradeoff to balance the required communication resource and the desired performance: Lowering the desired performance allows the network to allocate more limited bandwidth to other nodes in need. Finally, a numerical example is given to show the effectiveness of the proposed method.

Broadband Radar Cross-Section Reduction Using AMC Technology

Abstract: This paper presents the design, fabrication, and characterization of a planar broadband chessboard structure to reduce the radar cross-section (RCS) of an object. The chessboard -like configuration is formed by combining two artificial magnetic conductor (AMC) cells. The bandwidth limitations intrinsic to AMC structures are overcome in this work by properly selecting the phase slope versus frequency of both AMC structures. A 180 ° phase difference has been obtained over more than 40% frequency bandwidth with a RCS reduction larger than 10 dB. The influence of the incidence angle in the working bandwidth has been performed. A good agreement between simulations and measurements is achieved.

A Wideband, Wide Scanning Tightly Coupled Dipole Array With Integrated Balun (TCDA-IB)

Abstract: A key challenge in the design of wideband dipole phased arrays is the design of equally wideband baluns which are sufficiently compact to fit within the unit cell (typically in the linear dimension at low frequencies). In this paper, we exploit the reactance of a compact Marchand balun as an impedance matching network for each array element. The elimination of bulky external baluns results in a significant reduction of size, weight and cost, while the bandwidth is simultaneously improved by over 30%, compared to standard feeding techniques. In this manner, a tightly coupled dipole array with an integrated balun (TCDA-IB) is developed which achieves 7.35:1 bandwidth (0.68 - 5.0 GHz) while scanning to ±45° in all directions, subject to . In a dual-polarization configuration, the TCDA-IB has low cross polarization of over the majority of the band. Measured results are presented for a prototype 8 × 8 element TCDA-IB, showing good agreement with simulation.

Towards high-capacity fibre-optic communications at the speed of light in vacuum

Abstract: Wide-bandwidth signal transmission with low latency is emerging as a key requirement in a number of applications, including the development of future exaflop-scale supercomputers, financial algorithmic trading and cloud computing. Optical fibres provide unsurpassed transmission bandwidth, but light propagates 31% slower in a silica glass fibre than in vacuum, thus compromising latency. Air guidance in hollow-core fibres can reduce fibre latency very significantly. However, state-of-the-art technology cannot achieve the combined values of loss, bandwidth and mode-coupling characteristics required for high-capacity data transmission. Here, we report a fundamentally improved hollow-core photonic-bandgap fibre that provides a record combination of low loss (3.5 dB km-1) and wide bandwidth (160 nm), and use it to transmit 373 x 40 Gbit s-1 channels at a 1.54 ms km-1 faster speed than in a conventional fibre. This represents the first experimental demonstration of fibre-based wavelength division multiplexed data transmission at close to (99.7%) the speed of light in vacuum

Quantitative analysis of split base station processing and determination of advantageous architectures for LTE

Abstract: Centralization of the baseband processing in radio access networks may reduce radio site operations costs, reduce capital costs, and ease implementation of multi-site coordination mechanisms such as coordinated multipoint transmission and reception (CoMP). However, the initial architecture proposals for a centralized Long Term Evolution (LTE) deployment using transport of radio samples require a high-bandwidth, low-latency interconnection network. This may be uneconomical, or it may only be cost effective for a limited number of sites. To mitigate that deficiency without sacrificing the benefits of centralized processing, we identified alternative interfacing options between central and remote units. To do so we analyzed possible splits of the Long Term Evolution (LTE) baseband processing chain for their bandwidth and latency requirements. Next, we analyzed the operational impacts of potential splits based on a number of criteria including ease of CoMP introduction, the possibility of realizing pooling gains, and the ability to update the system and introduce new features. Based on our results, we propose architectures that can leverage the benefits of centralization at a much-reduced cost.

Optical sinc-shaped Nyquist pulses of exceptional quality

Abstract: Sinc-shaped Nyquist pulses possess a rectangular spectrum, enabling data to be encoded in a minimum spectral bandwidth and satisfying by essence the Nyquist criterion of zero inter-symbol interference (ISI). This property makes them very attractive for communication systems since data transmission rates can be maximized while the bandwidth usage is minimized. However, most of the pulse-shaping methods reported so far have remained rather complex and none has led to ideal sinc pulses. Here a method to produce sinc-shaped Nyquist pulses of very high quality is proposed based on the direct synthesis of a rectangular-shaped and phase-locked frequency comb. The method is highly flexible and can be easily integrated in communication systems, potentially offering a substantial increase in data transmission rates. Further, the high quality and wide tunability of the reported sinc-shaped pulses can also bring benefits to many other fields, such as microwave photonics, light storage and all-optical sampling.

All-fiber spectrometer based on speckle pattern reconstruction

Abstract: A standard multimode optical fiber can be used as a general purpose spectrometer after calibrating the wavelength dependent speckle patterns produced by interference between the guided modes of the fiber. A transmission matrix was used to store the calibration data and a robust algorithm was developed to reconstruct an arbitrary input spectrum in the presence of experimental noise. We demonstrate that a 20 meter long fiber can resolve two laser lines separated by only 8 pm. At the other extreme, we show that a 2 centimeter long fiber can measure a broadband continuous spectrum generated from a supercontinuum source. We investigate the effect of the fiber geometry on the spectral resolution and bandwidth, and also discuss the additional limitation on the bandwidth imposed by speckle contrast reduction when measuring dense spectra. Finally, we demonstrate a method to reduce the spectrum reconstruction error and increase the bandwidth by separately imaging the speckle patterns of orthogonal polarizations. The multimode fiber spectrometer is compact, lightweight, low cost, and provides high resolution with low loss.

Survey on broadband techniques for vibration energy harvesting

Abstract: Various energy harvesting systems have been proposed in the last years The use of ambient energy, such as vibration energy, has evoked great interests Most vibration-based converters generate the maximum power only when the generator is excited at its resonance frequency To overcome this limitation, researchers focus on strategies for increasing the working bandwidth of an energy harvester Due to the amount of different approaches for broadband energy harvesting, we suggest a categorization This review presents a classification of the current techniques Every technique has its own benefits and drawbacks and is suitable for different applications This review presents the categorization and describes each conversion technique Typical research approaches are shown to get a better understanding of the energy harvesting techniques The advantages and drawbacks are presented, and the suitability is shown for each category

Multimode optical fiber based spectrometers

Abstract: A standard multimode optical fiber can be used as a general purpose spectrometer after calibrating the wavelength dependent speckle patterns produced by interference between the guided modes of the fiber. A transmission matrix was used to store the calibration data and a robust algorithm was developed to reconstruct an arbitrary input spectrum in the presence of experimental noise. We demonstrate that a 20 meter long fiber can resolve two laser lines separated by only 8 pm. At the other extreme, we show that a 2 centimeter long fiber can measure a broadband continuous spectrum generated from a supercontinuum source. We investigate the effect of the fiber geometry on the spectral resolution and bandwidth, and also discuss the additional limitation on the bandwidth imposed by speckle contrast reduction when measuring dense spectra. Finally, we demonstrate a method to reduce the spectrum reconstruction error and increase the bandwidth by separately imaging the speckle patterns of orthogonal polarizations. The multimode fiber spectrometer is compact, lightweight, low cost, and provides high resolution with low loss.

High-Power Broadly Tunable Electrooptic Frequency Comb Generator

Abstract: Broadband traveling-wave electrooptic modulators made of lithium niobate have reached a high level of technological maturity. They can provide simultaneously low Vπ, sustain high power (both optical and RF) and yet provide low propagation loss. By combining together these features, we present a high-power handling, broadly tunable, electrooptic frequency comb generator. The device produces between 60 and 75 lines within -10 dB bandwidth over its full tuning range-from 6 to 18 GHz-and can handle up to 1 W of optical input power. This optical frequency comb platform is very well suited for applications in RF photonics and optical communications that require independent RF and optical tuning as well as high-repetition rates but moderate bandwidth.

Systems and methods for wireless communication in sub gigahertz bands

Abstract: Systems, methods, and devices for wireless communication. In one aspect, an apparatus for wireless communication is provided. The apparatus includes a receiver configured to receive a wireless signal comprising a packet. At least a portion of the wireless signal is configured to be received over a bandwidth lower than or equal to 1.25 MHz. The packet is formed from at least one orthogonal frequency-division multiplexing (OFDM) symbol comprising thirty-two tones. The thirty-two tones correspond to frequency subcarriers within the bandwidth. The thirty-two tones of the at least one OFDM symbol are allocated as: twenty-four data tones, two pilot tones, five guard tones, and one direct current (DC) tone. The apparatus includes a processor configured to evaluate the wireless signal. The processor includes a transform module configured to convert the at least one OFDM symbol into a frequency domain signal using a thirty-two point mode.

An IEEE 802.11a/g/p OFDM receiver for GNU radio

Abstract: Experimental research on wireless communication protocols frequently requires full access to all protocol layers, down to and including the physical layer. Software Defined Radio (SDR) hardware platforms, together with real-time signal processing frameworks, offer a basis to implement transceivers that can allow such experimentation and sophisticated measurements. We present a complete Orthogonal Frequency Division Multiplexing (OFDM) receiver implemented in GNU Radio and fitted for operation with an Ettus USRP N210. To the best of our knowledge, this is the first prototype of a GNU Radio based OFDM receiver for this technology. Our receiver comprises all layers up to parsing the MAC header and extracting the payload of IEEE 802.11a/g/p networks. It supports both WiFi with a bandwidth of 20 MHz and IEEE 802.11p DSRC with a bandwidth of 10 MHz. We validated and verified our implementation by means of interoperability tests, and present representative performance measurements. By making the code available as Open Source we provide an easy-to-access system that can be readily used for experimenting with novel signal processing algorithms.

Ultra-High-Contrast and Tunable-Bandwidth Filter Using Cascaded High-Order Silicon Microring Filters

Abstract: High-contrast optical filtering is demonstrated using cascaded silicon microrings. We report an experimental measurement of a record 100 dB pass-band to stop-band contrast, tunable 12–125 GHz passband full-width at half-maximum, band-center insertion loss ripple ${ , and a group delay ripple ${ , using transverse electric polarized light.

A 94 GHz mm-Wave-to-Baseband Pulsed-Radar Transceiver with Applications in Imaging and Gesture Recognition

Abstract: High-resolution mm-wave array beamformers have applications in medical imaging, gesture recognition, and navigation. A scalable array architecture for 3D imaging is proposed in which single-element phase coherent transceiver (TRX) chips, with programmable TX pulse delay capability, are mounted on a common board to realize the array. This paper presents the design of the enabling TRX chip: a highly integrated 94 GHz phase-coherent pulsed-radar with on-chip antennas. The TRX achieves 10 GHz of frequency tuning range and 300 ps of contiguous pulse position control, enabling its usage in the large-array imager with time-domain TX beamforming. The TRX is capable of transmitting and receiving pulses down to 36 ps, translating to 30 GHz of bandwidth. Interferometric measurements show the TRX can obtain single-target range resolution better than 375 μm (limited by equipment). Based on delay measurements, the time of arrival rms error would be less than 1.3 ps which, if used in a 3D imaging array, leads to less than 0.36 mm of RMS error in voxel size and position.

A Novel OFDM Chirp Waveform Scheme for Use of Multiple Transmitters in SAR

Abstract: In this letter, we present a new waveform technique for the use of multiple transmitters in synthetic aperture radar (SAR) data acquisition. This approach is based on the principle of the orthogonal-frequency-division-multiplexing technique. Unlike multiple subband approaches, the proposed scheme allows the generation of multiple orthogonal waveforms on common spectral support and thereby enables to exploit the full bandwidth for each waveform. This letter introduces the modulation and the demodulation processing in regard to typical spaceborne SAR receive signals. The proposed processing techniques are verified by a simulation for the case of pointlike targets.

Stochastic Model for Earthquake Ground Motion Using Wavelet Packets

Abstract: For performance-based design, non-linear dynamic structural analysis for various types of input ground motions is required. Stochastic (simulated) ground motions are sometimes useful as input motions, because unlike recorded motions they are not limited in number and because their properties can be varied systematically to understand the impact of ground motion properties on structural response. Here a stochastic ground motion model with time and frequency nonstationarity is developed using wavelet packets. Wavelet transform is a tool for analyzing time-series data with time and frequency nonstationarity, as well as simulating such data. Wavelet packet transform is an operation that decomposes time-series data into wavelet packets in the time and frequency domain, and its inverse transform reconstructs a time-series from wavelet packets. The characteristics of a nonstationary ground motion therefore can be modeled intuitively by specifying the amplitudes of wavelet packets at each time and frequency. In the proposed model, 13 parameters are sufficient to completely describe the time and frequency characteristics of a ground motion. These parameters can be computed from a specific target ground motion recording or by regression analysis based on a large database of recordings. The simulated ground motions produced by the proposed model reasonably match the target ground motion recordings in several respects including the spectral acceleration, inelastic response spectra, duration, bandwidth, and time and frequency nonstationarity. In addition, the median and logarithmic standard deviation of the spectral acceleration of the simulated ground motions match those of the published empirical ground motion prediction. These results suggest that the syntheti c ground motions generated by the proposed model can be used for the non-linear dynamic structural analysis as the input ground motions.

Modeling the Effect of Human Body on TOA Based Indoor Human Tracking

Abstract: In time-of-arrival (TOA) based indoor human tracking system, the human body mounted with the target sensor can cause non-line of sight (NLOS) scenario and result in significant ranging error. However, the previous studies on the behavior of indoor TOA ranging did not take the effects of human body into account. In this paper, measurement of TOA ranging error has been conducted in a typical indoor environment and sources of inaccuracy in TOA-based indoor localization have been analyzed. To quantitatively describe the TOA ranging error caused by human body, we introduce a statistical TOA ranging error model for body mounted sensors based on the measurement results. This model separates the ranging error into multipath error and NLOS error caused by the creeping wave phenomenon. Both multipath error and NLOS error are modeled as a Gaussian variable. The distribution of multipath error is only relative to the bandwidth of the system while the distribution of NLOS error is relative to the angle between human facing direction and the direction of transmitter–receiver, signal to noise ratio and bandwidth of the system, which clearly shows the effects of human body on TOA ranging.

An Active Disturbance Rejection Based Approach to Vibration Suppression in Two-Inertia Systems

Abstract: This study concerns the resonance problems found in motion control, typically described in a two-inertia system model as compliance between the motor and the load. We reformulate the problem in the framework of active disturbance rejection control (ADRC), where the resonance is assumed to be unknown and treated as disturbance, estimated and mitigated. This allows the closed-loop bandwidth to go well beyond the resonant frequency, which is quite difficult using existing methods. In addition, such level of performance is achieved with minimum complexity in the controller design and tuning: no parameter estimation or adaptive algorithm is needed, and the controller is tuned by adjusting one parameter, namely, the bandwidth of the control loop. It is also shown that the proposed solution applies to both the velocity and position control problems, and the fact that ADRC offers an effective and practical motion control solution, in the presence of unknown resonant frequency within the bandwidth of the control system. Finally, frequency response analysis is performed where stability margin is obtained before the simulation results are verified in the hardware experiments.

Novel Dual-Broadband Planar Antenna and Its Array for 2G/3G/LTE Base Stations

Abstract: A novel dual-broadband planar antenna is proposed for 2G/3G/LTE (4G) mobile communications. The proposed dual-broadband antenna consists of one element for the lower band and two elements for the upper band, making it possible to be arrayed without appearance of grating lobes in the upper band. The lower-band element comprises a pair of printed dipoles with a pair of parasitic elements for bandwidth enhancement. Two upper-band elements composed of two pairs of folded dipoles are nested inside the lower-band element, forming a compact arrayable antenna unit. The dual-broadband antenna achieves a bandwidth of 20% (800-980 MHz) for the lower band and a bandwidth of 60% (1540-2860 MHz) for the upper band. A dual-broadband antenna array that consists of 4 elements for the lower band and 8 elements for the upper band is developed for base station applications. The dual-broadband array achieves a bandwidth of 22% (780-980 MHz) for the lower band and a bandwidth of 68% (1470-3000 MHz) for the upper band, covering all the frequency bands for 2G/3G/LTE (4G) systems. Measured antenna gains for the array are ~12 dBi for the lower band and dBi for the upper band, suitable for potential applications in mobile communication base stations.

Germanium photodetector with 60 GHz bandwidth using inductive gain peaking

Abstract: Germanium-on-silicon photodetectors have been heavily investigated in recent years as a key component of CMOS-compatible integrated photonics platforms. It has previously been shown that detector bandwidths could theoretically be greatly increased with the incorporation of a carefully chosen inductor and capacitor in the photodetector circuit. Here, we show the experimental results of such a circuit that doubles the detector 3dB bandwidth to 60 GHz. These results suggest that gain peaking is a generally applicable tool for increasing detector bandwidth in practical photonics systems without requiring the difficult process of lowering detector capacitance.

Spectrally interleaved multi-carrier signals for radar network applications and multi-input multi-output radar

Abstract: A modification of the classical orthogonal frequency division multiplexing signals is discussed that allows for the creation of a set of perfectly orthogonal transmit signals sharing the same bandwidth. These signals can be employed for performing radar measurements with multiple transmitters being simultaneously active, for example, in radar networks or multi-input multi-output radar applications. Since all the signals of the individual transmitters occupy the full available bandwidth, no deterioration of the achievable range resolution occurs. This study comprises both the theoretical considerations as well as the verification simulations and measurements. A particular focus is on the requirements regarding the frequency and time synchronisation of the individual signals and their impact on the achievable performance. The influence of possible Doppler shifts is also considered. Finally, a performance comparison with classical code-based multiple user access techniques is provided. The achieved results demonstrate that the proposed multi-carrier waveforms clearly outperform the classical code-based approach under realistic assumptions of synchronisation accuracy.

A Reconfigurable Triple-Notch-Band Antenna Integrated with Defected Microstrip Structure Band-Stop Filter for Ultra-Wideband Cognitive Radio Applications

Abstract: A printed reconfigurable ultra-wideband (UWB) monopole antenna with triple narrow band-notched characteristics is proposed for cognitive radio applications in this paper. The triple narrow band-notched frequencies are obtained using a defected microstrip structure (DMS) band stop filter (BSF) embedded in the microstrip feed line and an inverted π-shaped slot etched in the rectangular radiation patch, respectively. Reconfigurable characteristics of the proposed cognitive radio antenna (CRA) are achieved by means of four ideal switches integrated on the DMS-BSF and the inverted π-shaped slot. The proposed UWB CRA can work at eight modes by controlling switches ON and OFF. Moreover, impedance bandwidth, design procedures, and radiation patterns are presented for analysis and explanation of this antenna. The designed antenna operates over the frequency band between 3.1 GHz and 14 GHz (bandwidth of 127.5%), with three notched bands from 4.2 GHz to 6.2 GHz (38.5%), 6.6 GHz to 7.0 GHz (6%), and 12.2 GHz to 14 GHz (13.7%). The antenna is successfully simulated, fabricated, and measured. The results show that it has wide impedance bandwidth, multimodes characteristics, stable gain, and omnidirectional radiation patterns.